1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to generating an adjustable chaotic signal, and more particularly, to generating an adjustable chaotic signal so as to reduce power consumption and to be capable of adjusting the center frequency and bandwidth.
2. Description of the Related Art
Recently, wireless communications methods using an ultra wideband (UWB) frequency band in a spectrum of 3.1 GHz to 5.1 GHz other than Bluetooth have developed, among which is a method for transmitting information using a chaotic signal proposed by the IEEE 802.15.4a standard.
IEEE 802.15.4a is a Low Rate Alternative physical layer protocol (PHY) Task Group, and is a combination of a 802.15.4 (Zigbee) and 802.15.3 (UWB) with location capability and low power functions.
What is proposed to implement in low power is a chaotic signal modulation method. The chaotic signal modulation method is designed with a simple RF hardware structure and does not need circuits, such as voltage controlled oscillators (VCOs), phase locked loops (PLLs) and mixers, required for conventional wireless communications systems. Accordingly, power consumption can be reduced to 10 mW, ⅓ of conventional power consumption.
The core of the chaotic signal modulation method is a chaotic signal generation device for generating wideband chaotic signals. Conventional chaotic signal generation devices generate a chaotic signal in a UWB of 3.1 GHz to 5.1 GHz, and switch the chaotic signal on and off in an On Off keying (OOK) modulation method to convert the signal into a chaotic carrier.
However, the chaotic signal generated by such chaotic signal generation devices is a single signal in the entire frequency band of a UWB. Thus, if a plurality of users use wireless devices in a particular wireless communications area, utilization of the same channel results in interference. Consequently, only a single wireless device can transmit and receive wireless signals at any given time in a particular wireless communications area. That is, it is impossible to use a frequency division multiplexing (FDM) method in which a plurality of users carry out communications using a plurality of frequency channels in a particular communications area.
Moreover, as a chaotic signal is generated in the entire frequency band of a UWB and requires high non-linearity of a power amplifier, power consumption is high.
Hence, what is needed is that a plurality of users can spontaneously carry out wireless communications within a particular wireless communications area by generating a chaotic signal according to a frequency band, that is, a channel, in a chaotic signal generation device, resulting in enabling application of a FDM method. Also, a method is required for reducing power consumption.